KR0153063B1 - Inhibition of food pathogens by hop acids - Google Patents

Abstract

The present invention relates to the protection of food from infection by food pathogens, specifically Listeria monocytogenes, by incorporating 6-50 ppm, preferably 6-15 ppm, of beta-acid extracted from hops into the food. .

Description

[Name of invention]

Inhibition method of food pathogen by hop acid

[Background of invention]

The present invention relates to the use of beta-acids extracted from hops for inhibiting Listeria and other food pathogens in food consumed by humans.

Recent studies have shown that Listeria monocytogenes and human Listeria monocytogenes, in particular, have been shown to affect the consumption of various types of foods, particularly soft cheeses and pies, as well as ham and other packaged meat and poultry products. Found to be relevant. Listeria Monocytogenes in Prepacked Ready-To-Eat Sliced Meats, PHLS Microbiology Digest Vol., A report by 16 public health laboratories at PHLS food chains in S. Velani and R. J. Gilbert. 7 (1990).

Hopes and their related acids have long been recognized as bacteriological inhibitors. More specifically, hop acids and resins are Gram-positive bacteria such as Bacilli, Corynebacteria, Diplococci, Mycobacteria, Streptococci, Lactobacilli and It has been shown to have primary activity against Streptomyces. Most publications focus on lactic acid bacteria, because this organism is the main infectious agent in beer fermentation. Less activity is known for Gram-negative bacteria. Teuber and Schmalrek, Arch. Mikrobiol. 94, pp. 159-171, 1973 and the Simpson and Hammond Convention (European Brewery Convention, 1991) are effective due to the permeability of cell membranes induced in Gram-positive bacteria, but inactivated by serum phospholipids in Gram-negative bacteria Presenting.

[Overview of invention]

The present invention relates to the discovery that beta-acids in high-mimic acids contained in hops are useful as fungicides against pathogens (listeria) for amounts not likely to be strongly tasted by beta-acids.

Detailed description of the invention

The bacteriostatic action, one of Hope's long-standing roles in beer production, was absolute in the modern production of beer by aseptic fermentation and packaging. Hope's high acid component and specifically beta-acid, have now been found to be unexpectedly useful as fungicides in food. The most potent groups of high mimic acids found as components of hops are alpha- and beta-acids, referred to as huulones and lupulones, respectively. Both of these contribute to beer as a bitter, but in this respect alpha-acid is much more potent than beta-acid. In addition, manufacturers of hop extracts have recently developed a technique for separating two acid fractions using liquid carbon dioxide under supercritical conditions. The byproduct of the operation is a product containing approximately 61% by weight of beta-acid and the residue consisting essentially of the hop resin.

The alpha-acids contained in the hops have the general formula:

Alpha-acids form precipitates by lead acetate.

Beta-acids contained in hops have the following general formula:

Beta-acids do not form precipitates by lead acetate.

As used herein, beta-acid is substantially insoluble in aqueous solutions below pH 5.2, but readily dissolves above pH 7. Thus, beta-acid is usually applied as an aqueous solution at pH 7-9.5 to the food to be treated. Generally, the aqueous solution contains 6 to 100 ppm of beta acid and most preferably 15 to 50 ppm. An aqueous solution of beta acid may be applied to the food to be treated as a spray and immersed in a solution of beta acid before storing the food.

Depending on the fermentation process and the type of hops used, the hops are added to the wort in an amount of 1 to 8 grams per liter during the brewing process. Generally, the hops contain 2 to 12% by weight alpha-acid and 1 to 10% by weight beta-acid. Thus the beta-acid content of wort is 0.001 to 0.08% by weight (10 to 800 ppm) of beta-acid. In general, for use herein, beta-acids are extracted to produce products containing 50-80% by weight of beta-acid, diluted or concentrated to produce the desired aqueous solution.

The present invention relates to the discovery that beta-acid rich carbon dioxide extract fractions are useful as food preservatives. The present invention aims at a food pathogen, Listeria monopsychogenis. The pathogen kills approximately 70 people per year, more than twice the number of any other food pathogen. In general, it is believed that the main cause of Listeria infection is food manufacturers. This leads to powerful research into new technologies for detecting and suppressing Listeria.

It has now been found that the growth of Listeria monocytogenes is completely inhibited in liquid medium at a concentration of 6 parts per million beta-acids (ppm). The experiments of the present inventors show that the effect is bacteriostatic. We also found beta-acids in Salmonella enteritidis (enterococci), Staphylococcus aureus (S. aureus) and Clostridium perfringes (Welch). Growth inhibition by In addition, Campylobactu sputorum bubulus, Sccharomyces cerevisieac (beer yeast), Aspergillus niger (black bacillus), Candida tropicalalis (Candidatropicalis) ), Geotrichum sp., Penicillium griseofulvum and Fusarium tricintum did not show any growth inhibition by beta-acid.

The evaluation of taste indicates that the purified beta-acid has a strong taste above 15 ppm and an unpleasant taste above 50 ppm. Thus, in general, to protect against infection by Listeria, beta-acid is applied in foods in an amount of 6 to 50 ppm, most preferably 6 to 15 ppm (by weight of the food).

Foods that can usually be infected by Listeria are solid foods, including cheese, in particular soft cheeses, seafood and processed meats including hot dogs, sausages, hams, turkeys and chickens.

EXAMPLE

Example 1

1.0 g samples of the beta-acid fraction were weighed and placed in large test tubes. The beta-acid fraction is a product sold by the Rohm and Hass Company and was obtained by Hoff's liquid carbon dioxide extract under supercritical conditions. The beta-acid fraction contained 61% beta-acid and the residue was essentially hop resin. 5 ml of hexane was added to the test tube and the contents of the test tube were shaken to dissolve beta-acid.

15 ml of 1 M aqueous NaOH was added to the test tube and the contents of the test tube were shaken well. The alkaline aqueous phase was slowly poured over and removed and stored. Another 15 ml of 1M aqueous NaOH was added to the test tube and the contents of the test tube were shaken well. The alkaline aqueous phase was slowly poured off and combined with the stored alkaline aqueous phase. The combined alkaline aqueous phase material was acidified to about pH 1 with concentrated hydrochloric acid. The acidified aqueous phase was then extracted three times with 125 ml of petroleum ether using a separatory funnel. The solution of beta-acid is dried over sodium sulfate at 23 to 24 ° C. and then the experimental apparatus roto-bag at 45 ° C. (Roto-Vac ), Excess ether was removed until only oily residue remained. The oil was placed in the freezer at -20 ° C. Isolation by filtration to form crystals, which were then recrystallized from ether at -20 ° C. Beta-acid was stored in the freezer until use.

Example 2

Most test tubes contain 5 ml of brain-heart juice (B-H juice). Test tubes were inoculated with 100 microliters of Listeria culture grown overnight in B-H broth. A solution of beta-acids prepared in Example 1 was added to each test tube to give the beta-acid concentrations shown in Table 2 below. Another set of test tubes containing concentrated B-H broth and beta-acids was prepared according to the above preparation method. These latter test tubes were not inoculated with Listeria. All test tubes were incubated together at 35 ° C. for 24 hours.

As shown in the table above, beta-acid has an effective bacteriostatic activity against Listeria in an amount of about 5 ppm or more.

In Table 2, the column for NG / growth represents the value for the number of dishes, or the number of live colonies per ml of medium. Lawn or TNTC designations represent more than 300 colonies per ml.

Example 3

A solution containing 100 ppm of beta-acids was prepared as follows.

10 mg of the beta-acid solution of Example 1 was placed in a 45 ml sterile test tube. 10 ml of 95% ethyl alcohol was added to the test tube to dissolve beta-acid. The resulting solution was added to a 100 ml flask. The contents of the flask were made up to 100 ml in total with 8.5 pH Mueller Hinton Broth. The resulting solution was filtered under sterile conditions using a filter of pore size 0.45U. The filtered beta-acid solution ml and 1.6 ml Mueller Hinton broth were added to a sterile 125 ml shake flask with a stir bar. 20 ml of Mueller Hinton broth were added to each of 18 50 ml test tubes with sufficient beta-acid solution prepared above to the amount of beta-acid shown in Table 3. After all the tubes were filled, 2.5 ml were removed from each tube to record the pH. Nine test tubes were inoculated with 25U Listeria Mueller Hinton Bolot (6N). All 18 test tubes were incubated at 35 ° C. for 24 hours. OD (600 nm) and pH were recorded after incubation for 24 hours. The results are shown in Table 3.

Example 4

A solution containing 100 ppm beta-acids was prepared as follows:

10 mg of the beta-acid solution of Example 1 was placed in a 45 ml sterile test tube. 10 ml of 95% ethyl alcohol was added to the test tube to dissolve beta-acid. The resulting solution was added to a 100 ml flask. The contents of the flask were made up to 100 ml in total with 8.5 pH Mueller Hinton broth. The resulting solution was filtered under sterile conditions using a filter of pore size 0.45 Um. Filtered beta-acid solution ml and 1.6 ml of BH broth were added to a sterile 125 ml shake flask equipped with a stir bar. 20 ml of BH gravy were added to each of 18 50 ml test tubes with sufficient beta-acid solution prepared above to bring the amounts of beta-acids shown in Table 4. After all the tubes were filled, 2.5 ml were removed from each tube to record the pH. Nine test tubes were inoculated with 25 Ul Listeria in BH broth (6N). All 18 test tubes were incubated at 35 ° C. for 24 hours. OD (600 nm) and pH were recorded after incubation for 24 hours. The results are shown in Table 4.

In this example, O.D was obtained at 600 nm using 2.5 ml of well mixed juicy in disposable cavette.

The results indicate that beta-acid inhibits the growth of Listeria below 6 ppm for both Mueller Hinton and B-H gravy.

pH is influenced by the concentration of beta-acids, but is independent of the growth rate of Listeria. Thus, pH does not concern the inhibition of growth of Listeria as observed herein.

Claims (7)

In order to inhibit the growth of Listeria in a solid food, a solution containing 6 to 100 ppm of beta-acid extracted from a hop to incorporate 6-50 ppm of beta-acid in the food is included. How to. The method of claim 1, wherein the solution of beta-acid is applied to the food by immersing the food in the solution of beta-acid. The method of claim 2, wherein 6 to 15 ppm of beta-acid is incorporated into the food. The method of claim 1, wherein the solution of beta-acid is applied to the food by spraying the solution of beta-acid onto the food. The method of claim 4, wherein 6 to 15 ppm of beta-acid is incorporated into the food. A packaged solid food containing 6-50 ppm of beta-acid extracted from hops to inhibit the growth of Listeria in a solid food. 7. A food product according to claim 6 containing 6 to 15 ppm of beta-acid.